[Objectives]  To study the relative infectiousness of six fungal strains isolated from different parts of Cordyceps sinensis to Hepialus armoricanus larvae. C. sinensis-related fungi are defined as fungi isolated from wild C. sinensis that can infect and kill H. armoricanus larvae and interact with O. sinensis. [Methods]  Biological characteristics of 6 strains of related fungi were described and their ITS sequences were aligned to identify the species. The infectiveness of the six strains of related fungi to H. armoricanus larvae were tested separately. Two related fungi were tested in a joint infection experiment with O. sinensis. [Results]  The 6 strains of related fungi all affected the growth of O. sinensis: The inhibition rate of the 2F-2, FD, TB-1 and TB-4 strains to O. sinensis was close to 100%, that of the 3-5-2 strain was 4.32% and that of the MR-1 strain was 77.27%. All six strains had the ability to infect H. armoricanus larvae. The infection rate of the 3-5-2 strain was 50.0%, that of the 2F-2 strain was 85.0% and that of the MR-1 strain was 73.3%. The infection rate of FD strain was 70.0%; the infection rate of the TB-1 strain was 64.0% and the infection rate of the TB-4 strain was 65.0%. The mortality rate of joint infections was lower than that of single-strain infections. [Conclusion]  The 6 strains of related fungi were all infectious to H. armoricanus larvae and can interact with O. sinensis.